In California, a state where water has become a scarce commodity, San Francisco is a pioneer in the reuse of water in an effort to reduce consumption among residents. The installation of on-site non-potable water reuse systems for storm water, rain water and gray water has contributed to consumption falling to some of the lowest per capita levels in the state. An ordinance requires new buildings of a certain size to use the system for anything that does not require potable water, such as toilets and cooling towers. Paula Kehoe, Director of Water Resources at the San Francisco Public Utilities Commission (SFPUC), explains the public multi-utility’s strategy in an interview with “We Build Value”.
Your water system in San Francisco is one of the most pioneering in the country. Can you explain briefly how it works?
«The San Francisco Public Utilities Commission provides three utility
services: water, power and sewer. For nearly 100 years, we have been
providing San Francisco Bay Area residents and businesses high-quality
drinking water. Today, we serve 2.7 million people in four Bay Area
Our Regional Water System is complex. It includes three watersheds, 11 reservoirs, five pump stations, and two water treatment plants. The distribution infrastructure includes over 280 miles of pipeline and 60 miles of tunnels traveling over 167 miles, crossing four county lines and three major earthquake faults. It takes a fleet of well-qualified and dedicated operators and engineers of the SFPUC to deliver water from this system safely and reliably to our customers every single day.
While we face increasing risks and challenges to our water supply due to a variety of concerns, such as earthquakes, droughts, regulatory changes and population growth, we are working harder than ever to ensure a resilient water supply for the next hundred years. One major initiative is the $4.8 billion Water System Improvement Program, which is designed to improve our seismic and drought reliability as well as water quality improvements and water supply diversification».
How has the recent drought changed your focus on water management?
«As California is prone to droughts, it is important to consider water conservation as a way of life. Since the early 1990s, we recognized the need to establish a conservation program and to enhance local water supplies. Decades of promoting conservation has led to a per capita water use in San Francisco of 42 gallons per person per day which is among the lowest in the United States. We are supplementing our surface water supplies with groundwater, recycled water and non-potable water to enhance water supply reliability and resiliency».
What are some of your most innovative projects?
«Through OneWaterSF, we have cultivated a shift in thinking about
water and energy resource management. OneWaterSF has allowed us to move
away from operating within traditional water, wastewater and energy
boundaries to a more holistic resource management approach that enables
us to better recognize, value and utilize our resources.
As a leader in pioneering new technologies to reduce water use and to reuse water, our headquarters incorporates an onsite, decentralized water system and exemplifies OneWaterSF. The innovative constructed wetland systems, located in the sidewalks around and inside the building, treats roughly 5,000 gallons of blackwater each day for toilet and urinal flushing, reducing our potable water demands in the building by 60 percent.
The pioneering reuse project at our headquarters was the impetus behind one of the nation’s most cutting-edge onsite water reuse programs. Our Non-potable Water Program allows for the collection, treatment and reuse of rainwater, stormwater, graywater and blackwater at a building or district-scale. Today, all new developments over 250,000 square feet in San Francisco are required to treat their own water onsite to meet their toilet flushing and irrigation demands».
Do other cities do this too?
«Onsite non-potable water systems have been installed in cities throughout the world-New York, Seattle, Tokyo, Sydney and others. However, San Francisco’s program is unique in that it streamlines the permitting process for developers and incorporates water standards that are health risk based to protect public health. As with any emerging strategy, the field of practice for onsite non-potable water reuse is still taking shape. That’s why we established the National Blue Ribbon Commission for Onsite Non-potable Water Systems to advance best management practices to support the use of onsite non-potable water systems across the United States. We’ve made significant research contributions and advanced policies and regulations for onsite water reuse enabling jurisdictions to move forward with programs to advance implementation of onsite systems, including California, Colorado, Minnesota, Texas, and Alaska».
With this legislation, you have spearheaded San Francisco’s pioneering adoption of on-site non-potable water treatment systems. How do they work? How much water can be saved?
«The design and operational complexity of an onsite non-potable water
system will vary depending on the water source and end use. In all
cases, the technology exists to treat water for non-potable uses within a
small footprint and in a manner that protects public health. A common
treatment technology for rainwater is ultraviolet light disinfection
whereas a treatment system for blackwater may consist of a membrane bio
reactor, ultraviolet light disinfection, and chlorine.
Onsite treated water can be used for a variety of non-potable uses within and outside building. Replacing the demand for toilet and urinal flushing with non-potable water can offset approximately 25 percent of the total potable water use in a residential building, and up to 75 percent in a commercial building. Other potential non-potable demands include irrigation, cooling/heating applications, process water and clothes washing. Using onsite treatment systems to meet these demands can further reduce potable water demands by a total of 50 to 90 percent».
Any other innovative projects going on?
«We are continuing to look to the future by leading a cutting-edge effort to test the feasibility of purified water for San Francisco. We have initiated a 9-month pilot project that takes treated water from our onsite water treatment system within the SFPUC’s building and further treats it to meet drinking water standards. The pilot uses ultrafiltration, reverse osmosis, and advanced oxidation with ultraviolet lights. After data collection, the water will be returned to the building for toilet flushing. The pilot has three main objectives: 1) see how consistently and reliably the technology works, 2) gather in-depth water quality data and 3) engage our communities on potable reuse. PureWaterSF is supported by grants from the Water Research Foundation and the U.S. Bureau of Reclamation».
What are the future projects you are working towards now?
«We’ve recently expanded on onsite program to allow breweries to capture and treat process water onsite for reuse. This effort required us to develop a tailored chemical and pathogen control strategy for breweries. We anticipate local breweries moving forward with onsite treatment systems and we see this as an exciting opportunity to reduce the amount of water used in beer making as on average its takes five gallons of water to produce one gallon of beer».
How is this $4.8 billion rolling capital improvement plan split between public and private sources?
«The majority of our capital improvement program is funded by our ratepayers and our wholesale customers. We have received a few grants and seek low interest loans for our capital projects. For example, we received loan and grant for a recycled water project from the State Water Resources Control Board’s Clean Water State Revolving Fund which will save $123 million for our ratepayers».
Have you noticed a change in attitude of the community and stakeholders in recent years around conservation issues?
«We value our long-standing partnerships that we have established with the diverse communities that we serve. Water is serious, but it doesn’t have to be humorless. We look for unconventional ways to engage the public. For example, to get people on board with 10 percent water conservation goals, we launched a public education campaign to show that water conservation is smart and sexy, to capture public attention and present water conservation tips and information about the drought. We went from a residential per capita water use of 185 liters per day in 2013 to 155 liters per day in 2016».